Problem: $ { \left[\begin{array}{rrr}{-1} & {-2} & {-2} \\ {-1} & {1} & {0}\end{array}\right]+\left[\begin{array}{rrr}{2} & {-1} & {3} \\ {-2} & {-1} & {1}\end{array}\right] = {?} } $
Answer: To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rrr}{-1}+{2} & {-2}+{-1} & {-2}+{3} \\ {-1}+{-2} & {1}+{-1} & {0}+{1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{1} & {-3} & {1} \\ {-3} & {0} & {1}\end{array}\right]}$